/*
 * Copyright (C) 2007 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect;

import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.VisibleForTesting;

import javax.annotation.CheckForNull;

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Implementation of {@link ImmutableSet} with two or more elements.
 *
 * @author Kevin Bourrillion
 */
@GwtCompatible(serializable = true, emulated = true)
@SuppressWarnings("serial") // uses writeReplace(), not default serialization
@ElementTypesAreNonnullByDefault
final class RegularImmutableSet<E> extends ImmutableSet<E>
{
    private static final Object[] EMPTY_ARRAY = new Object[0];
    static final RegularImmutableSet<Object> EMPTY =
            new RegularImmutableSet<>(EMPTY_ARRAY, 0, EMPTY_ARRAY, 0, 0);

    // The first `size` elements are non-null.
    @VisibleForTesting
    final transient @Nullable
    Object[] elements;
    private final transient int hashCode;
    // the same values as `elements` in hashed positions (plus nulls)
    @VisibleForTesting
    final transient @Nullable
    Object[] table;
    // 'and' with an int to get a valid table index.
    private final transient int mask;
    private final transient int size;

    RegularImmutableSet(
            @Nullable Object[] elements, int hashCode, @Nullable Object[] table, int mask, int size)
    {
        this.elements = elements;
        this.hashCode = hashCode;
        this.table = table;
        this.mask = mask;
        this.size = size;
    }

    @Override
    public boolean contains(@CheckForNull Object target)
    {
        @Nullable Object[] table = this.table;
        if (target == null || table.length == 0)
        {
            return false;
        }
        for (int i = Hashing.smearedHash(target); ; i++)
        {
            i &= mask;
            Object candidate = table[i];
            if (candidate == null)
            {
                return false;
            }
            else if (candidate.equals(target))
            {
                return true;
            }
        }
    }

    @Override
    public int size()
    {
        return size;
    }

    @Override
    public UnmodifiableIterator<E> iterator()
    {
        return asList().iterator();
    }

    @Override
    @Nullable
    Object[] internalArray()
    {
        return elements;
    }

    @Override
    int internalArrayStart()
    {
        return 0;
    }

    @Override
    int internalArrayEnd()
    {
        return size;
    }

    @Override
    int copyIntoArray(@Nullable Object[] dst, int offset)
    {
        System.arraycopy(elements, 0, dst, offset, size);
        return offset + size;
    }

    @Override
    ImmutableList<E> createAsList()
    {
        return ImmutableList.asImmutableList(elements, size);
    }

    @Override
    boolean isPartialView()
    {
        return false;
    }

    @Override
    public int hashCode()
    {
        return hashCode;
    }

    @Override
    boolean isHashCodeFast()
    {
        return true;
    }
}
